A Bonspiel is a curling tournament, consisting of several games, often held on a weekend. Until the 20th century most bonspiels were held outdoors, on a frozen freshwater loch. Today almost all bonspiels are held indoors on specially prepared artificial ice. Though it is not mandatory, curling teams at bonspiels often wear themed costumes.

Bonspiels originated in Scotland, the most notable competitive curling tournament in the world nowadays is The Brier, the Canadian Men's Curling Championship. For Canadians, this tournament equals or nearly equals the importance of the Olympics and the World Curling Championship[citation needed]. The Canadian Women's Curling Championship tournament is called Scotties Tournament of Hearts. Several Cashspiels are played in Canada every year. The most important cashspiels are part of the World Curling Tour (WCT). Many local curling clubs and other organizations in Canada also host casual, social bonspiels.

The United States Curling Association (USA Curling) is the national governing body of the sport in the United States. Many bonspiels are listed on the USA Curling website. Most bonspiels in the United States are held indoors in dedicated curling facilities. Bonspiels are popular throughout the United States during curling season, typically October through April. Some special bonspiels are held in the summer as well as some that are hosted by clubs that play on arena ice as there are usually fewer scheduling conflicts with other sports at the area such as hockey and figure skating.

In Scotland, outdoor bonspiels are now very rare; most lochs that formerly hosted bonspiels, such as Loch Earn, rarely freeze over anymore. The word spiel is sometimes used to refer to an informal curling game, as in parish spiel. The most important Cashspiels in Scotland are part of the Curling Champions Tour (CCT), previously known as the World Curling Tour Europe (WCT-E).

Curling bonspiels are held when ice conditions permit in the Maniototo, part of Central Otago in the South Island. The region is one of the few in New Zealand to have conditions suitable for outdoor curling, and is also a fitting site for the sport given that Otago's original European settlers were mainly from Scotland. Several artificial and natural lakes around the towns of Oturehua, Naseby and Patearoa provide good conditions, on average every second or third year.

The national bonspiel has been held when conditions permit since 1879, with Oturehua's Idaburn Dam the venue since 1932.[1] The most recent national bonspiel, the 65th, was held on 9–10 July 2012.[2] Owing to the difficulty of getting teams to the relatively inaccessible venue, it is rare for teams to travel from outside the southern South Island to the bonspiel.

The largest outdoor bonspiel in the world, the "Ironman Outdoor Curling Bonspiel" held on the Assiniboine River in Winnipeg, Manitoba, Canada, has been held at The Forks Historic Port every February since 2002. In 2015 there were 72 teams competing.

One of the longest-running outdoor bonspiels in the world, the Bonspiel on the Lake in Invermere, British Columbia, Canada, has been held on Lake Windermere every January since 1982. Each year 64 teams compete.

The Bonspiel or the Grand Match, between the north and the south of Scotland, is held on a frozen loch (most recently the Lake of Menteith, Stirling) when the winter is cold enough. It was last held in 1979.

"The Crush Bonspiel" in Placer Valley, California, is notorious for its unique combination of tournament play and wine festival. This tournament originated in Vacaville in 2006 but was moved to Roseville in 2012 because of its rising popularity in surrounding areas.

Since curling is believed to have originated in Scotland, it is likely that "bonspiel" is a modern adaptation of the Scottish Gaelic words "bonn" (coin)[4] and "spéil" (skate)[5] meaning "coin skate" or "cornerstone skate" (archaic definition).[6]

"Spiel" may also have been a Germanic borrowing, meaning "game". In that case, the word may have meant "cornerstone game".